Current breaker circuit for storage devices, voltage detection circuit for storage devices and abnormality detection circuit

ABSTRACT

A current breaker circuit by which currents flowing in loads respectively connected to a plurality of storage devices B 1  to B 4  connected in series are broken in accordance with a single external control signal. The current breaker circuit includes semiconductor switching devices Q 1  to Q 4  inserted between the storage devices and the loads respectively, a unit S for supplying the external control signal to at least one of the semiconductor switching devices, and control signal generating units q 1  to q 3  for generating ON/OFF signals in accordance with turning ON/OFF of the semiconductor switching device supplied with the external control signal so as to supply the ON/OFF signals to the other semiconductor switching devices.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a current breaker circuit forcutting off a plurality of storage devices connected in series, and loadcircuits (voltage detection circuit) for the respective storage devicesin accordance with a single external signal so that a leakage currentcan be prevented; to a voltage detection circuit for such storagedevices; and an abnormality detection circuit.

[0002] In a circuit in which a plurality of storage devices areconnected in series and loads are connected to the storage devicesrespectively, it has been heretofore necessary to prevent consumption ofenergy accumulated in the storage devices.

[0003] To this end, there have been related-art current breaker circuitsas shown in FIGS. 6 and 7. Such current breaker circuits can disconnectall the loads in accordance with a single control signal when thestorage devices and the loads are disconnected respectively.

[0004] The configurations and operations of the related-art circuitswill be described below with reference to FIGS. 6 and 7.

[0005]FIG. 6 shows an example of a related-art current breaker circuit.

[0006] In FIG. 6, storage devices B1 to B4 are connected in series. Inaddition, loads R1 to R4 are connected to the storage devices B1 to B4respectively.

[0007] In addition, semiconductor switching devices Q1 to Q4 areconnected between the storage devices B1 to B4 and the loads R1 to R4respectively.

[0008] The bases of the semiconductor switching devices Q1 to Q4 whichare control terminals are connected in common through diodes d1 to d4and resistors r1 to r4 so that an external signal switch S providedbetween the common connection terminal and the negative terminal of thestorage device B1 can be turned ON or OFF in accordance with an ON/OFFsignal.

[0009] As for the operation of this current breaker circuit, when theexternal signal switch S provided between the common connection terminalof the resistors r1 to r4 and the negative terminal of the storagedevice B1 is turned ON in accordance with the ON/OFF signal supplied tothe switch S, all the semiconductor switching devices Q1 to Q4 areturned ON. Thus, currents are supplied from the storage devices B1 to B4to the loads R1 to R4 corresponding and respectively.

[0010] On the contrary, when the external signal switch S is turned OFF,the semiconductor switching devices Q1 to Q4 are turned OFF so that nocurrent is supplied to the loads R1 to R4.

[0011] In this current breaker circuit, all the semiconductor switchingdevices Q1 to Q4 can be turned ON/OFF in accordance with a single ON/OFFsignal. However, on the higher potential side (the storage device B4side in FIG. 6) of the storage devices connected in series, the voltagebetween the emitter of the semiconductor switching device and thenegative terminal of the storage device B1 increases. Thus, there is aproblem that the power loss of the resistor increases and a high voltageswitch has to be used as the external signal switch S.

[0012]FIG. 7 shows another example of a related-art current breakercircuit.

[0013] In FIG. 7, storage devices B1 to B4 are connected in series inthe same manner as those in FIG. 6.

[0014] In addition, loads R1 to R4 are connected to the storage devicesB1 to B4 respectively.

[0015] In addition, photo-couplers (photo-relays) PH1 to PH4 areconnected between the storage devices B1 to B4 and the loads R1 to R4respectively.

[0016] All of light-emitting diodes of the photo-couplers PH1 to PH4 areconnected in series, and designed so that a current is supplied betweenopposite terminals of each light-emitting diode in accordance with anON/OFF signal given to the switch S.

[0017] As for the operation of this current breaker circuit, all thephoto-couplers PH1 to PH4 are turned ON when a current is supplied tothe light-emitting diodes connected in series. Thus, currents aresupplied from the storage devices B1 to B4 to the loads R1 to R4respectively.

[0018] On the contrary, when no current is supplied to thelight-emitting diodes connected in series, all the photo-couplers PH1 toPH4 are turned OFF. Thus, no current is supplied to the loads R1 to R4.

[0019] In this current breaker circuit, all the semiconductor switchingdevices Q1 to Q4 can be turned ON/OFF in accordance with a single ON/OFFsignal. Accordingly, the problem of withstanding voltage as in thecircuit of FIG. 6 is solved. On the other hand, there is however aproblem that a large number of expensive photo-couplers or the like haveto be used.

SUMMARY OF THE INVENTION

[0020] In order to solve the defects in the related-art current breakercircuits, an object of the invention is to provide a current breakercircuit which can surely break currents supplied to a plurality of loadsfrom a plurality of storage devices connected in series, in accordancewith a single external control signal without using any high-voltagewithstanding switch or any expensive photo-coupler; and to provide avoltage detection circuit for such storage devices.

[0021] In addition, another object of the invention is to provide anabnormality detection circuit for such a current breaker circuit.

[0022] To solve the foregoing problems, according to the invention,there is provided a current breaker circuit for storage devices by whichcurrents flowing in loads are broken in accordance with a singleexternal control signal, while the loads are connected between terminalsof a plurality of storage devices connected in series respectively. Thecurrent breaker circuit includes semiconductor switching devicesinserted between the storage devices and the loads respectively, a unitfor supplying the external control signal to at least one of thesemiconductor switching devices, and a control signal generating unitfor generating an ON/OFF signal in response to an electric change basedon turning ON/OFF of the semiconductor switching device supplied withthe external control signal, the ON/OFF signal being supplied to othersemiconductor switching devices.

[0023] Accordingly, currents supplied from the plurality of storagedevices connected in series to the plurality of loads can be surelybroken in accordance with a single external control signal without usingany high-voltage withstanding switch or any expensive photo-coupler.

[0024] The loads in this configuration may be formed as pieces of avoltage detection circuit for storage devices. In this case, the currentbreaker circuit for storage devices has features in that:

[0025] (1) a plurality of storage devices are connected in series;

[0026] (2) a piece of the voltage detection circuit is connected forevery unit cell of the plurality of storage devices;

[0027] (3) each piece of the voltage detection circuit is connectedbetween a positive terminal and a negative terminal of a correspondingunit cell of the plurality of storage devices;

[0028] (4) a semiconductor switching device is inserted between thestorage device and the voltage detection circuit;

[0029] (5) a control signal generator circuit for supplying a controlsignal to a control electrode of the semiconductor switching deviceinserted in series is connected to the control electrode of thesemiconductor switching device; and

[0030] (6) the control signal generator circuit detects a voltage changeon the voltage detection circuit side of the semiconductor switchingdevices connected to the storage devices other than the storage deviceto which the semiconductor switching device for supplying the controlsignal is connected, and the control signal generator circuit generatesthe control signal in accordance with the detection of the voltagechange.

[0031] In addition, when the external control signal is supplied to atleast two adjacent ones of the semiconductor switching devicessimultaneously, the current breaker circuit for storage devices can beformed out of a smaller number of constituent members.

[0032] In addition, when the control signal generating unit supplies theON/OFF signal to at least two adjacent ones of the semiconductorswitching devices simultaneously, the number of the control signalgenerator circuits can be reduced.

[0033] In addition, when the semiconductor switching device suppliedwith the external control signal is formed as a semiconductor switchingdevice connected to a lower voltage side among the storage devicesconnected in series, the potential of the switch can be made lower.

[0034] In addition, when the ON/OFF signal is supplied to thesemiconductor switching devices through diodes respectively, highvoltage can be prevented from being applied to the control terminals ofthe semiconductor switching devices.

[0035] In addition, when the loads are formed as a voltage detectioncircuit for detecting terminal-to-terminal voltages of the plurality ofstorage devices connected in series, even a very small current flowingin the voltage detection circuit can be broken surely.

[0036] Further, a voltage detection circuit for storage devicesaccording to the invention has features in that:

[0037] a plurality of terminal-to-terminal voltage generator circuitsare provided;

[0038] each of the terminal-to-terminal voltage generator circuits isconstituted by a storage device, a subtractor circuit and an A/Dconverter circuit, the subtractor circuit being supplied with a positiveterminal voltage (Vn+1) and a negative terminal voltage (Vn) of thestorage device and outputting a terminal-to-terminal voltage (Vno) ofthe storage device, the A/D converter circuit being supplied with theoutput of the subtractor circuit and outputting digital data;

[0039] the storage devices provided in the plurality ofterminal-to-terminal voltage generator circuits are connected in series;

[0040] outputs of the A/D converter circuits provided in the pluralityof terminal-to-terminal voltage generator circuits are supplied to aselector circuit, which selects one piece of output data from theparallel output data supplied from the plurality of A/D convertercircuits; and

[0041] the selected piece of output data is supplied to aparallel-to-serial converter circuit, which converts the piece of outputdata into serial data, and outputs the converted serial data, so that aterminal-to-terminal voltage of any desired one of the plurality ofstorage devices connected in series is obtained as the serial data.

[0042] In the voltage detection circuit for storage devices configuredthus, the terminal-to-terminal voltages of the plurality of storagedevices connected in series can be detected accurately and selectivelyrespectively to be outputted.

[0043] In addition, an external select control signal may be supplied tothe selector circuit.

[0044] In addition, a plurality of parallel-to-serial converter circuitsmay be provided at a pre-stage of the selector circuit so that theselector circuit can select one from the outputs converted into serialdata by the parallel-to-serial converter circuits.

[0045] In addition, when the serial data and/or the select controlsignal are supplied through an isolator, the serial data and/or theselect control signal can be electrically isolated from externalcircuits.

[0046] Further, a voltage detection circuit for storage devicesaccording to the invention has features in that:

[0047] at least a plurality of terminal-to-terminal voltage generatorcircuits are provided;

[0048] each of the terminal-to-terminal voltage generator circuits isconstituted by a storage device, a subtractor circuit and an A/Dconverter circuit, the subtractor circuit being supplied with a positiveterminal voltage (Vn+1) and a negative terminal voltage (Vn) of thestorage device and outputting a terminal-to-terminal voltage (Vno) ofthe storage device, the A/D converter circuit being supplied with theoutput of the subtractor circuit and outputting digital data;

[0049] the storage devices provided in the plurality ofterminal-to-terminal voltage generator circuits are connected in series;

[0050] a selector circuit selects one piece of output data from outputdata of the A/D converter circuits respectively provided in theplurality of terminal-to-terminal voltage generator circuits; and

[0051] the selected piece of output data is supplied to aparallel-to-serial converter circuit, which converts the supplied pieceof output data into serial data;

[0052] the terminal-to-terminal voltage generator circuits, the selectorcircuit and the parallel-to-serial converter circuit are included in asingle module; and

[0053] a pair of opposite terminals of the plurality of storage devicesconnected in series, and an output terminal of the serial data are ledout as external terminals of the module.

[0054] When the single module is configured thus, a desired system canbe constructed easily by use of a plurality of such modules.

[0055] In addition, when a select control signal from the outside of themodule is supplied as a serial signal to the selector circuit, signalscan be transmitted/received between the module and the outside through asmall number of signal lines.

[0056] In addition, a plurality of parallel-to-serial converter circuitsmay be provided at a pre-stage of the selector circuit so that theselector circuit can select one from the outputs converted into serialdata by the parallel-to-serial converter circuits.

[0057] In addition, an isolator for electrically isolating the serialdata and/or the select control signal may be provided in the module.

[0058] Further, according to the invention, an abnormality detectioncircuit for detecting abnormality of a current breaker circuit breakingcurrents in accordance with a single external control signal isprovided. The currents flow into a plurality of loads which arerespectively connected between terminals of a plurality of storagedevices connected in series. When operation abnormality of the currentbreaker circuit is detected on the basis of the single external controlsignal and a terminal-to-terminal voltage of a final-stage one of theloads in the abnormality detection circuit, abnormality of the operationof the current breaker circuit as a whole can be detected easily.

[0059] In addition, a first photo-coupler and a second photo-coupler maybe provided and connected in series to opposite terminals of thefinal-stage load respectively. In this case, the external control signalis supplied to the second photo-coupler only for an abnormalitydetection period so as to turn on the abnormality detection circuit andthereby obtain a detection result through the first photo-coupler. Thus,a current is allowed to flow into a light emitting device of the firstphoto-coupler and a light receiving device of the second photo-coupleronly for the detection period. Accordingly, it is not necessary to makea constant conduction. It is therefore possible to prevent uselessconsumption of electric power.

BRIEF DESCRIPTION OF THE DRAWINGS

[0060]FIG. 1 is a diagram showing the configuration of a first currentbreaker circuit according to the invention.

[0061]FIG. 2 is a diagram showing the configuration of a second currentbreaker circuit according to the invention.

[0062]FIG. 3 is a diagram showing an abnormality detection circuit for acurrent breaker circuit according to the invention.

[0063]FIG. 4 is a diagram showing the details of a voltage detectioncircuit according to the invention.

[0064]FIG. 5 is a diagram showing the details of another voltagedetection circuit according to the invention.

[0065]FIG. 6 is a diagram showing the configuration of a related-artcurrent breaker circuit.

[0066]FIG. 7 is a diagram showing the configuration of anotherrelated-art current breaker circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0067] Embodiments of the invention will be described below withreference to the drawings.

[0068]FIG. 1 is a diagram showing a current breaker circuit according toa first embodiment of the invention.

[0069] In FIG. 1, storage devices B1 to B4 are connected in series.

[0070] In addition, loads R1 to R4 are connected to the storage devicesB1 to B4 respectively.

[0071] In addition, semiconductor switching devices Q1 to Q4 areconnected between the storage devices B1 to B4 and the loads R1 to R4respectively.

[0072] The base of the semiconductor switching device (e.g. transistoror FET) Q1 which is a control terminal is connected to one end of aswitch S through a resistor r1. The switch S is turned ON/OFF inaccordance with an external control signal.

[0073] Further, the base of the semiconductor switching device Q2 whichis a control terminal is connected to the collector of a transistor q1through a resistor r2. The transistor q1 constitutes a control signalgenerator circuit.

[0074] The base of the transistor q1 is connected to the collector ofthe semiconductor switching device Q1 through a resistor r11, while theemitter of the transistor q1 is connected to the negative terminal ofthe load R1.

[0075] In addition, the base of the semiconductor switching device Q3which is a control terminal is connected to the collector of atransistor q2 through a resistor r3. The transistor q2 constitutes acontrol signal generator circuit.

[0076] The base of the transistor q2 is connected to the collector ofthe semiconductor switching device Q2 through a resistor r22, while theemitter of the transistor q2 is connected to the negative terminal ofthe load R2.

[0077] In addition, the base of the semiconductor switching device Q4which is a control terminal is connected to the collector of atransistor q3 through a resistor r4. The transistor q3 constitutes acontrol signal generator circuit.

[0078] The base of the transistor q3 is connected to the collector ofthe semiconductor switching device Q3 through a resistor r33, while theemitter of the transistor q3 is connected to the negative terminal ofthe load R3.

[0079] The current breaker circuit shown in FIG. 1 operates as follows.

[0080] First, when the switch S is turned ON in accordance with anexternal control signal, a current flows from the emitter to the base inthe semiconductor switching device Q1. Thus, the semiconductor switchingdevice Q1 is turned ON.

[0081] When the semiconductor switching device Q1 is turned ON, acurrent from the collector of the semiconductor switching device Q1flows from the base to the emitter in the transistor q1 whichconstitutes a control signal generator circuit. Thus, the transistor q1is turned ON.

[0082] Then, when the transistor q1 is turned ON, a current flows fromthe emitter to the base in the semiconductor switching device Q2. Thus,the semiconductor switching device Q2 is turned ON.

[0083] Further, when the semiconductor switching device Q2 is turned ON,a current from the collector of the semiconductor switching device Q2flows from the base to the emitter in the transistor q2 whichconstitutes a control signal generator circuit. Thus, the transistor q2is turned ON.

[0084] Then, when the transistor q2 is turned ON, a current flows fromthe emitter to the base in the semiconductor switching device Q3. Thus,the semiconductor switching device Q3 is turned ON.

[0085] Further, when the semiconductor switching device Q3 is turned ON,a current from the collector of the semiconductor switching device Q3flows from the base to the emitter in the transistor q3 whichconstitutes a control signal generator circuit. Thus, the transistor q3is turned ON.

[0086] Then, when the transistor q3 is turned ON, a current flows fromthe emitter to the base in the semiconductor switching device Q4. Thus,the semiconductor switching device Q4 is turned ON.

[0087] In such a manner, when the switch S is turned ON in accordancewith an external control signal, all the semiconductor switching devicesQ1 to Q4 are turned ON.

[0088] On the contrary, when the switch S is turned OFF in accordancewith an external control signal, no current flows from the emitter tothe base in the semiconductor switching device Q1. Thus, thesemiconductor switching device Q1 is turned OFF.

[0089] When the semiconductor switching device Q1 is turned OFF, thetransistors q1 to q3 which constitute control signal generator circuitsrespectively are not allowed to be turned ON, so that all thesemiconductor switching devices Q1 to Q4 are turned OFF.

[0090] In such a manner, in the current breaker circuit shown in FIG. 1according to the first embodiment, all the semiconductor switchingdevices Q1 to Q4 are allowed to be turned ON/OFF in accordance with asingle external control single (ON/OFF signal). Thus, the currentbreaker circuit can be constructed without using any high-voltagewithstanding switch, any expensive photo-coupler, or the like.

[0091]FIG. 2 is a diagram showing a current breaker circuit according toa second embodiment of the invention.

[0092] In FIG. 2, storage devices B1 to B4 are connected in series.

[0093] In addition, loads R1 to R4 are connected to the storage devicesB1 to B4 respectively.

[0094] In addition, semiconductor switching devices Q1 to Q4 areconnected between the storage devices B1 to B4 and the loads R1 to R4respectively.

[0095] The bases of the semiconductor switching devices Q1 and Q2 whichare control terminals are connected to one end of a switch S throughseries circuits of resistors r1 and r2 and diodes d1 and d2respectively. The switch S is turned ON/OFF in accordance with anexternal control signal.

[0096] In addition, the bases of the semiconductor switching devices Q3and Q4 which are control terminals are connected to the collector of atransistor q1 through series circuits of resistors r3 and r4 and diodesd3 and d4 respectively. The transistor q1 constitutes control signalgenerator circuits.

[0097] The base of the transistor q1 is connected to the collector ofthe semiconductor switching device Q2 through a resistor r11, while theemitter of the transistor q1 is connected to the negative terminal ofthe load R2.

[0098] The current breaker circuit shown in FIG. 2 operates as follows.

[0099] First, when the switch S is turned ON in accordance with anexternal control signal, a current flows from the emitter to the base ineach of the semiconductor switching devices Q1 and Q2. Thus, both thesemiconductor switching devices Q1 and Q2 are turned ON.

[0100] When the semiconductor switching devices Q1 and Q2 are turned ON,a current from the collector of the semiconductor switching device Q2flows from the base to the emitter in the transistor q1 whichconstitutes the control signal generator circuit. Thus, the transistorq1 is turned ON.

[0101] Then, when the transistor q1 is turned ON, a current flows fromthe emitter to the base in each of the semiconductor switching devicesQ3 and Q4. Thus, the semiconductor switching devices Q3 and Q4 areturned ON.

[0102] In such a manner, when the switch S is turned ON in accordancewith an external control signal, all the semiconductor switching devicesQ1 to Q4 are turned ON.

[0103] On the contrary, when the switch S is turned OFF in accordancewith an external control signal, the semiconductor switching devices Q1and Q2 are turned OFF because no current flows from the emitter to thebase of each of the semiconductor switching devices Q1 and Q2.

[0104] When the semiconductor switching device Q2 is turned OFF, thetransistor q1 constituting the respective control signal generatorcircuits cannot be turned ON. Thus, all the semiconductor switchingdevices Q1 to Q4 are turned OFF.

[0105] In such a manner, in the current breaker circuit according to thefirst embodiment as shown in FIG. 2, all the semiconductor switchingdevices Q1 to Q4 can be turned ON/OFF in accordance with a singleexternal control signal (ON/OFF signal). In addition, the currentbreaker circuit can be constructed without using any high-voltagewithstanding switch or any expensive photo-coupler or the like. At thesame time, since two semiconductor switching devices are turned ON/OFFin common, the number of control signal generator circuits can bereduced.

[0106] Incidentally, although two semiconductor switching devices areturned ON/OFF in common in FIG. 2, two or more semiconductor switchingdevices may be turned ON/OFF in common in accordance with thewithstanding voltages of the respective devices.

[0107] Although the current breaker circuits in FIGS. 1 and 2 aredescribed on the assumption that currents from a plurality of storagedevices connected in series are supplied to loads through a plurality ofsemiconductor switching devices, higher effect can be obtained if theloads provided in this case are formed as a voltage detection circuitfor detecting individual terminal-to-terminal voltages of the storagedevices.

[0108] In a system using a plurality of storage devices connected inseries, even when the system is down, currents flow, though slightly,into the voltage detection circuit (corresponding to the loads in FIGS.1 and 2) for detecting terminal-to-terminal voltages of the plurality ofstorage devices connected in series.

[0109] When such a state continues for a long time, currents arereleased from the storage devices. Therefore, when the system is down,it is necessary to break currents flowing into the voltage detectioncircuit.

[0110] In such a case, the current breaker circuits shown in FIGS. 1 and2 are effective in preventing the storage devices from discharging whenan external control signal is generated in response to the system down.

[0111] Further, the current breaker circuit shown in FIG. 1 or 2 may beformed into a module as a unit block. In this case, lower-voltage-sideand higher-voltage side terminals of the plurality of storage devicesconnected in series, control terminals for the semiconductor switchingdevices, and an output terminal corresponding to the electric continuityof the semiconductor switching devices are provided outside the unitmodule. When a plurality of such modules are connected in cascade, asystem adapted to any desired voltage can be constructed.

[0112] Also in this case, a plurality of semiconductor switching deviceslying over the plurality of modules in the system can be turned ON/OFFin accordance with a single external signal.

[0113]FIG. 3 is a diagram showing an abnormality detection circuit for acurrent breaker circuit according to a third embodiment of theinvention.

[0114] In FIG. 3, storage devices B1 to B4 are connected in series.

[0115] In addition, loads R1 to R4 are connected to the storage devicesB1 to B4 respectively.

[0116] In addition, semiconductor switching devices Q1 to Q4 areconnected between the storage devices B1 to B4 and the loads R1 to R4respectively.

[0117] The base of the semiconductor switching device (e.g. transistoror FET) Q1 which is a control terminal is connected to be supplied withthe output of a photo-coupler PH3 which is turned ON/OFF in accordancewith an external control signal c.

[0118] Further, the base of the semiconductor switching device Q2 whichis a control terminal is connected to the collector of a transistor q1through a resistor. The transistor q1 constitutes a control signalgenerator circuit.

[0119] The base of the transistor q1 is voltage-divided by resistors andconnected to the opposite ends of the load R1.

[0120] In addition, the base of the semiconductor switching device Q3which is a control terminal is connected to the collector of atransistor q2 through a resistor. The transistor q2 constitutes acontrol signal generator circuit.

[0121] The base of the transistor q2 is voltage-divided by resistors andconnected to the opposite ends of the load R2.

[0122] In addition, the base of the semiconductor switching device Q4which is a control terminal is connected to the collector of atransistor q3 through a resistor. The transistor q3 constitutes acontrol signal generator circuit.

[0123] The base of the transistor q3 is voltage-divided by resistors andconnected to the opposite ends of the load R3.

[0124] In addition, a transistor q4 constitutes a control signalgenerator circuit. The collector of the transistor q4 is led out to beconnected to a next-stage semiconductor switching device.

[0125] The base of the transistor q4 is voltage-divided by resistors andconnected to the opposite ends of the load R4.

[0126] Further, a light emitting device of a photo-coupler PH1 and alight receiving device of a photo-coupler PH2 are connected in series tothe opposite ends of the final-stage load R4 through a resistor.

[0127] A signal b is supplied to the light receiving device of thephoto-coupler PH2 while an output signal a is extracted from the lightreceiving device of the photo-coupler PH1.

[0128] Next, the operation of the abnormality detection circuit for thecurrent breaker circuit will be described.

[0129] In accordance with whether there is a signal c supplied to alight emitting device of a photo-coupler PH3 or not, the light emittingdevice is turned ON/OFF so that the semiconductor switching devices Q1to Q4 are turned ON/OFF sequentially in the same manner as in FIG. 1.

[0130] The signal b is designed to be supplied to the photo-coupler PH2only for a period for detecting whether there is a signal a from thephoto-coupler PH1 or not. Thus, the useless consumption of electricpower is prevented.

[0131] If the signal a is obtained (if the light receiving device of thephoto-coupler PH1 is turned ON) at the time when the signal c is present(at the time when a current is made to flow into the light emittingdevice of the photo-coupler PH3), this abnormality detection circuit canconclude that the current breaker circuit operates normally.

[0132] Further, if the signal a is obtained (if the light receivingdevice of the photo-coupler PH1 is turned OFF) at the time when thesignal c is present (at the time when a current is made to flow into thelight emitting device of the photo-coupler PH3), the abnormalitydetection circuit can conclude that the current breaker circuit isabnormal.

[0133] Further, if the signal a is obtained (if the light receivingdevice of the photo-coupler PH1 is turned ON) at the time when thesignal c is absent (at the time when no current is made to flow into thelight emitting device of the photo-coupler PH3), the abnormalitydetection circuit can conclude that the current breaker circuit isabnormal.

[0134] Further, if the signal a is obtained (if the light receivingdevice of the photo-coupler PH1 is turned OFF) at the time when thesignal c is absent (at the time when no current is made to flow into thelight emitting device of the photo-coupler PH3), the abnormalitydetection circuit can conclude that the current breaker circuit operatesnormally.

[0135] On the basis of the results of these four cases, the abnormalitydetection circuit can judge whether the current breaker circuit isnormal or abnormal.

[0136] Next, with reference to FIG. 4, description will be made on thedetails of a voltage detection circuit which is an example of loads onthe current breaker circuit.

[0137] In a module in which a plurality of storage devices have beenconnected thus in series, the terminal-to-terminal voltages of thestorage devices change individually. Therefore, a voltage detectioncircuit for detecting an accurate terminal-to-terminal voltage of eachstorage device is required.

[0138]FIG. 4 is a voltage detection circuit for detecting individualterminal-to-terminal voltages of a plurality of storage devices of astorage device group in which the storage devices have been connected inseries.

[0139] In FIG. 4, the reference signs B1 to B4 represent storage devicesconnected in series. Terminal-to-terminal voltage generator circuits VP1to VP4 are connected between positive terminals and negative terminalsof the storage devices respectively. An output is selected from theoutputs of the terminal-to-terminal voltage generator circuits by aselector circuit SE which is, for example, constituted by amulti-switchable IC and so on. The selected output is supplied through aparallel-to-serial converter circuit P/S.

[0140] In addition, the terminal-to-terminal voltage generator circuitsVP2 to VP4 are constituted by subtractor circuits D2 to D4 andanalog-to-digital converter circuits A/D2 to A/D4, which are constitutedby operational amplifiers and so on, respectively.

[0141] Incidentally, in the terminal-to-terminal voltage generatorcircuit VP1 to be connected to a lower-voltage-side storage device, thepositive terminal voltage of the storage device B1 is connected to ananalog-to-digital converter circuit A/D1 without passing through anysubtractor circuit.

[0142] Incidentally, also when the terminal-to-terminal voltagegenerator circuit VP1 to be connected to a lower-voltage-side storagedevice is connected to the analog-to-digital converter circuit A/D1through a subtractor circuit, similar operation can be carried out.

[0143] In each of the subtractor circuits D2 to D4, the negativeterminal voltage of the storage device to which the subtractor circuitis connected is subtracted from the positive terminal voltage thereof sothat the terminal-to-terminal voltage of the storage device is detected.

[0144] The detected terminal-to-terminal voltages of the storage devicesB1 to B4 are supplied to the selector circuit SE through theircorresponding analog-to-digital converter circuits A/D1 to A/D4respectively. The detected voltage of a storage device selected by theselector circuit SE is outputted as serial data through theparallel-to-serial converter circuit P/S.

[0145] Incidentally, though not shown in FIG. 4, it is effective thatthe output of the parallel-to-serial converter circuit P/S is suppliedthrough an isolator such as a photo-coupler. In this case, the outputcan be electrically isolated from the storage devices.

[0146] In addition, the detected voltages of the plurality of storagedevices B1 to B4 may be outputted selectively in a predetermined orderin the selector circuit by a CPU or the like. Alternatively, a detectedvoltage of a desired storage device may be outputted in accordance witha not-shown external select control signal.

[0147] In addition, the contents of data to be outputted as serial datamay include not only the terminal-to-terminal voltage of the detectedstorage device but also overvoltage or undervoltage information of therespective storage devices.

[0148] In addition, although description in FIG. 4 has be made on thecase where the detected voltage selected by the selector circuit isconverted into a serial signal by the parallel-to-serial convertercircuit, a plurality of parallel-to-serial converter circuits may beprovided so that detected voltages are converted into serial signalsbefore one is selected from the serial signals by the selector circuit.

[0149]FIG. 5 shows another example of a voltage detection circuit fordetecting individual terminal-to-terminal voltages of a plurality ofstorage devices of a storage device group in which the storage deviceshave been connected in series.

[0150] In FIG. 5, the reference signs B1 to B4 represent storage devicesconnected in series. Terminal-to-terminal voltage generator circuits VP1to VP4 are connected between positive terminals and negative terminalsof the storage devices respectively. An output is selected from theoutputs of the terminal-to-terminal voltage generator circuits by aselector circuit SE. The selected output is supplied through aparallel-to-serial converter circuit P/S. (In FIG. 5, theparallel-to-serial converter circuit P/S to be supplied with the outputof the selector circuit SE is not shown).

[0151] In addition, the terminal-to-terminal voltage generator circuitsVP2 to VP4 are constituted by subtractor circuits D2 to D4 andanalog-to-digital converter circuits A/D2 to A/D4, which are constitutedby operational amplifiers and so on, respectively.

[0152] Incidentally, in the terminal-to-terminal voltage generatorcircuit VP1 to be connected to a lower-voltage-side storage device, thepositive terminal voltage of the storage device B1 is connected to ananalog-to-digital converter circuit A/D1 without passing through anysubtractor circuit.

[0153] Incidentally, also when the terminal-to-terminal voltagegenerator circuit VP1 to be connected to a lower-voltage-side storagedevice is connected to the analog-to-digital converter circuit A/D1through a subtractor circuit, similar operation can be carried out.

[0154] In each of the subtractor circuits D2 to D4, the negativeterminal voltage of the storage device to which the subtractor circuitis connected is subtracted from the positive terminal voltage thereof sothat the terminal-to-terminal voltage of the storage device is detected.

[0155] The detected terminal-to-terminal voltages of the storage devicesB1 to B4 are supplied to the selector circuit SE through theircorresponding analog-to-digital converter circuits A/D1 to A/D4respectively. The detected voltage of a storage device selected by theselector circuit SE is outputted as serial data from the not-shownparallel-to-serial converter circuit P/S through an isolator PH (shownin the upper of FIG. 5) such as a photo-coupler.

[0156] In addition, in the selector circuit SE, a control command isgiven from the outside to a sub-controller SC through an isolator PH(shown in the lower of FIG. 5) such as a photo-coupler. By the outputfrom the sub-controller SC, the selector circuit SE is controlled tooutput detected voltages of a plurality of storage devices to theoutside.

[0157] It is effective that signals are inputted or outputted through anisolator such as a photo-coupler because the storage devices can beelectrically isolated from external circuits.

[0158] In addition, it is desired that the region of the voltagedetection circuit shown in FIG. 5 by the chain line, including theplurality of storage devices connected in series, is formed as onemodule.

[0159] In addition, the components of the voltage detection circuit inFIG. 5 including the subtractors, the analog-to-digital convertercircuits and the selector circuit are supplied with operating voltagesources from the storage devices in the module respectively, asillustrated.

[0160] When the circuit of FIG. 5 is formed as one module, a pair ofopposite terminals of the plurality of storage devices connected inseries, a signal output terminal from the selector circuit and a signalinput terminal for giving a command to the selector circuit from theoutside are provided outside the module.

[0161] In addition, when the voltage detection circuit of FIG. 5 isformed into a module, it can be chosen whether the isolators PHconstituted by photo-couplers or the like are provided inside the moduleor outside the module.

[0162] When a plurality of modules shown in FIG. 5 are connected inseries or in parallel, a desired system adapted to the voltage andcurrent for applications can be formed.

[0163] Further, although the number of storage devices to be connectedin series is four in FIGS. 1 to 5, not to say, a desired number ofstorage devices may be connected.

[0164] Incidentally, although the plurality of storage devices B1 to B4and the terminal-to-terminal voltage generator circuits are connecteddirectly in the voltage detection circuit in each of FIGS. 4 and 5,semiconductor switching devices maybe inserted between the storagedevices and their corresponding terminal-to-terminal voltage generatorcircuits respectively. In this case, the configuration as shown in FIGS.1 and 2 may be adopted so that a plurality of semiconductor switchingdevices can be turned ON/OFF in accordance with a single externalsignal.

[0165] As described above, according to the invention, there is provideda current breaker circuit for storage devices by which currents flowingin loads are broken in accordance with a single external control signal,while the loads are connected between terminals of a plurality ofstorage devices connected in series, respectively. The current breakercircuit includes semiconductor switching devices inserted between thestorage devices and the loads respectively, a unit for supplying theexternal control signal to at least one of the semiconductor switchingdevices, and a control signal generating unit for generating an ON/OFFsignal in response to an electric change based on turning ON/OFF of thesemiconductor switching device supplied with the external controlsignal, the ON/OFF signal being supplied to other semiconductorswitching devices. Accordingly, there is an effect that currentssupplied to the plurality of loads from the plurality of storage devicesconnected in series can be surely broken in accordance with a singleexternal control signal without using any high-voltage withstandingswitch or any expensive photo-coupler.

[0166] In addition, according to the invention, the external controlsignal is supplied to at least two adjacent ones of the semiconductorswitching devices simultaneously. Accordingly, the current breakercircuit for storage devices can be formed out of a smaller number ofconstituent members.

[0167] In addition, according to the invention, the control signalgenerating unit supplies the ON/OFF signal to at least two adjacent onesof the semiconductor switching devices simultaneously. Accordingly, thenumber of control signal generator circuits can be reduced.

[0168] In addition, according to the invention, the semiconductorswitching device supplied with the external control signal is formed asa semiconductor switching device connected to a lower voltage side amongthe storage devices connected in series. Accordingly, the potential withwhich the switch is connected can be made lower.

[0169] In addition, according to the invention, the ON/OFF signal issupplied to the semiconductor switching devices through diodesrespectively. Accordingly, high voltage can be prevented from beingapplied to the control terminals of the semiconductor switching devices.

[0170] Particularly, when the ON/OFF signal is designed to be suppliedsimultaneously to at least two adjacent ones of the semiconductorswitching devices connected in series, there is an effect that thesemiconductor switching devices are prevented from being broken.

[0171] In addition, according to the invention, the loads are formed asa voltage detection circuit for detecting terminal-to-terminal voltagesof the plurality of storage devices connected in series. Accordingly,even a very small current supplied to the voltage detection circuit canbe broken surely.

[0172] Further, a voltage detection circuit for storage devicesaccording to the invention is designed so that:

[0173] a plurality of terminal-to-terminal voltage generator circuitsare provided;

[0174] each of the terminal-to-terminal voltage generator circuits isconstituted by a storage device, a subtractor circuit and an A/Dconverter circuit, the subtractor circuit being supplied with a positiveterminal voltage (Vn+1) and a negative terminal voltage (Vn) of thestorage device and outputting a terminal-to-terminal voltage (Vno) ofthe storage device, the A/D converter circuit being supplied with theoutput of the subtractor circuit and outputting digital data;

[0175] the storage devices provided in the plurality ofterminal-to-terminal voltage generator circuits are connected in series;

[0176] outputs of the A/D converter circuits provided respectively inthe plurality of terminal-to-terminal voltage generator circuits aresupplied to a selector circuit, which selects one piece of output datafrom the parallel output data supplied from the plurality of A/Dconverter circuits; and

[0177] the selected piece of output data is supplied to aparallel-to-serial converter circuit, which converts the supplied pieceof output data into serial data, and outputs the converted serial data,so that a terminal-to-terminal voltage of any desired one of theplurality of storage devices connected in series is obtained as theserial data.

[0178] In the voltage detection circuit for storage devices configuredthus, the terminal-to-terminal voltages of the plurality of storagedevices connected in series can be detected accurately and selectivelyrespectively to be outputted.

[0179] In addition, according to the invention, an external selectcontrol signal is supplied to the selector circuit. Accordingly, theterminal-to-terminal voltage of a desired one of the storage devices canbe outputted in accordance with an external instruction.

[0180] In addition, according to the invention, a plurality ofparallel-to-serial converter circuits may be provided at a pre-stage ofthe selector circuit so that the selector circuit can select one fromthe outputs converted into serial data by the parallel-to-serialconverter circuits.

[0181] In addition, according to the invention, the serial data and/orthe select control signal are supplied through an isolator. Accordingly,the serial data and/or the select control signal can be electricallyisolated from external circuits.

[0182] Further, a voltage detection circuit for storage devicesaccording to the invention is formed so that:

[0183] at least a plurality of terminal-to-terminal voltage generatorcircuits are provided;

[0184] each of the terminal-to-terminal voltage generator circuits isconstituted by a storage device, a subtractor circuit and an A/Dconverter circuit, the subtractor circuit being supplied with a positiveterminal voltage (Vn+1) and a negative terminal voltage (Vn) of thestorage device and outputting a terminal-to-terminal voltage (Vno) ofthe storage device, the A/D converter circuit being supplied with theoutput of the subtractor circuit and outputting digital data;

[0185] the storage devices provided in the plurality ofterminal-to-terminal voltage generator circuits are connected in series;

[0186] a selector circuit selects one piece of output data from outputdata of the A/D converter circuits respectively provided in theplurality of terminal-to-terminal voltage generator circuits;

[0187] the selected piece of output data is supplied to aparallel-to-serial converter circuit, which converts the supplied pieceof output data into serial data;

[0188] the terminal-to-terminal voltage generator circuits, the selectorcircuit and the parallel-to-serial converter circuit are included in asingle module; and

[0189] a pair of opposite terminals of the plurality of storage devicesconnected in series, and an output terminal of the serial data are ledout as external terminals of the module.

[0190] Since the unit module is formed thus, a desired system can beconstructed easily by use of a plurality of such modules.

[0191] In addition, according to the invention, a select control signalfrom the outside of the module is supplied as a serial signal to theselector circuit. Accordingly, signals can be transmitted/receivedbetween the module and the outside through a small number of signallines.

[0192] In addition, according to the invention, a plurality ofparallel-to-serial converter circuits may be provided at a pre-stage ofthe selector circuit so that the selector circuit can select one fromthe outputs converted into serial data by the parallel-to-serialconverter circuits.

[0193] In addition, according to the invention, an isolator forelectrically isolating the serial data and/or the select control signalmay be provided in the module.

[0194] Further, according to the invention, an abnormality detectioncircuit for detecting abnormality of a current breaker circuit breakingcurrents in accordance with a single external control signal isprovided. The currents flow into a plurality of loads which arerespectively connected between terminals of a plurality of storagedevices connected in series. In the abnormality detection circuit,operation abnormality of the current breaker circuit is detected on thebasis of the single external control signal and a terminal-to-terminalvoltage of a final-stage one of the loads, so that abnormality of theoperation of the current breaker circuit as a whole can be detectedeasily.

[0195] In addition, according to the invention, a first photo-couplerand a second photo-coupler may be provided and connected to oppositeterminals of the final-stage load respectively. In this case, theexternal control signal is supplied to the second photo-coupler only foran abnormality detection period so as to turn on the abnormalitydetection circuit and thereby obtain a detection result through thefirst photo-coupler. Thus, a current is allowed to flow into a lightemitting device of the first photo-coupler and a light receiving deviceof the second photo-coupler only for the detection period. Accordingly,it is not necessary to make a constant conduction. It is thereforepossible to prevent useless consumption of electric power.

What is claimed is:
 1. A current breaker circuit for storage devices bywhich currents flowing in loads are broken in accordance with a singleexternal control signal, said loads being connected respectively betweenterminals of a plurality of storage devices connected in series, saidcurrent breaker circuit comprising: semiconductor switching devicesinserted between said storage devices and said loads respectively; aunit for supplying the external control signal to at least one of saidsemiconductor switching devices; and a control signal generating unitfor generating an ON/OFF signal in response to an electric change basedon turning ON/OFF of said semiconductor switching device supplied withthe external control signal, so as to supply the ON/OFF signal to othersemiconductor switching devices.
 2. The current breaker circuit forstorage devices according to claim 1, wherein the external controlsignal is supplied to at least two adjacent ones of said semiconductorswitching devices simultaneously.
 3. The current breaker circuit forstorage devices according to claim 1, wherein said control signalgenerating unit supplies the ON/OFF signal to at least two adjacent onesof said semiconductor switching devices.
 4. The current breaker circuitfor storage devices according to claim 1, wherein said semiconductorswitching device supplied with the external control signal is asemiconductor switching device connected to a lower voltage side amongsaid storage devices connected in series.
 5. The current breaker circuitfor storage devices according to claim 1, wherein the ON/OFF signal issupplied to said semiconductor switching devices through diodesrespectively.
 6. The current breaker circuit for storage devicesaccording to claim 1, wherein said loads are formed as a voltagedetection circuit for detecting terminal-to-terminal voltages of saidplurality of storage devices connected in series.
 7. A voltage detectioncircuit for storage devices, comprising: a plurality ofterminal-to-terminal voltage generator circuits each including a storagedevice, a subtractor circuit and an A/D converter circuit, saidsubtractor circuit being supplied with a positive terminal voltage(Vn+l) and a negative terminal voltage (Vn) of said storage device andoutputting a terminal-to-terminal voltage (Vno) of said storage device,said A/D converter circuit being supplied with said output of saidsubtractor circuit and outputting digital data, said storage devicesprovided in said plurality of terminal-to-terminal voltage generatorcircuits being connected in series; a selector circuit supplied withparallel output data from said plurality of A/D converter circuitsrespectively provided in said plurality of terminal-to-terminal voltagegenerator circuits, and selecting one piece of output data from saidparallel output data; and a parallel-to-serial converter circuitsupplied with said selected piece of output data from said selectorcircuit, converting said supplied piece of output data into serial data,and outputting said converted serial data, so that aterminal-to-terminal voltage of any desired one of said plurality ofstorage devices connected in series is obtained as said serial data. 8.The voltage detection circuit for storage devices according to claim 7,wherein an external select control signal is supplied to said selectorcircuit.
 9. The voltage detection circuit for storage devices accordingto claim 7, further comprising: a plurality of parallel-to-serialconverter circuits provided at a pre-stage of said selector circuit,wherein said selector circuit selects one from outputs of saidparallel-to-serial converter circuits converted into serial data. 10.The voltage detection circuit for storage devices according to claim 7,wherein the serial data and/or the select control signal are suppliedthrough an isolator.
 11. A voltage detection circuit for storagedevices, comprising: a plurality of terminal-to-terminal voltagegenerator circuits each including a storage device, a subtractor circuitand an A/D converter circuit, said subtractor circuit being suppliedwith a positive terminal voltage (Vn+1) and a negative terminal voltage(Vn) of said storage device and outputting a terminal-to-terminalvoltage (Vno) of said storage device, said A/D converter circuit beingsupplied with said output of said subtractor circuit and outputtingdigital data, said storage devices provided in said plurality ofterminal-to-terminal voltage generator circuits being connected inseries; a selector circuit supplied with output data from said pluralityof A/D converter circuits respectively provided in said plurality ofterminal-to-terminal voltage generator circuits, and selecting one pieceof output data from said supplied output data; and a parallel-to-serialconverter circuit supplied with said selected piece of output data fromsaid selector circuit, converting said selected piece of output datainto serial data, and outputting said converted serial data; whereinsaid terminal-to-terminal voltage generator circuits, said selectorcircuit and said parallel-to-serial converter circuit are included in asingle module; and a pair of opposite terminals of said plurality ofstorage devices connected in series, and an output terminal of saidserial data are led out as external terminals of said module.
 12. Thevoltage detection circuit for storage devices according to claim 11,wherein a select control signal from an outside of said module issupplied as a serial signal to said selector circuit.
 13. The voltagedetection circuit for storage devices according to claim 11, furthercomprising: a plurality of parallel-to-serial converter circuits areprovided at a pre-stage of said selector circuit, wherein said selectorcircuit selects one from outputs of said parallel-to-serial convertercircuits converted into serial data.
 14. The voltage detection circuitfor storage devices according to claim 11, wherein an isolator forelectrically isolating the serial data and/or the select control signalis provided in said module.
 15. An abnormality detection circuit fordetecting abnormality of a current breaker circuit for breaking currentsin accordance with a single external control signal, said currentsflowing into a plurality of loads which are respectively connectedbetween terminals of a plurality of storage devices connected in series,wherein operation abnormality of said current breaker circuit isdetected on the basis of the single external control signal and aterminal-to-terminal voltage of a final-stage one of said loads. 16.Then abnormality detection circuit according to claim 15, furthercomprising: a first photo-coupler and a second photo-coupler providedand connected to opposite terminals of said final-stage loadrespectively, wherein the external control signal is supplied to saidsecond photo-coupler only for an abnormality detection period so as toturn on said abnormality detection circuit and obtain a detection resultthrough said first photo-coupler.